The present invention relates generally to acoustic imaging and, more specifically, to systems and methods for acoustic imaging.
Acoustic imaging has been conventionally used in various material testing or measurement applications. For example, ultrasonic imaging has been used in non-destructive testing applications such as the testing of the properties of manufactured materials (e.g., testing for corrosion in aircraft wings). Ultrasonic imaging has further been used in medical imaging applications such as human soft tissue diagnosis. Conventional systems used to perform ultrasonic testing suffer from a number of disadvantages, such as system complexity and lack of image resolution.
U.S. Pat. No. 5,212,571 to Garlick et al., the disclosure of which is hereby incorporated by reference in its entirety, discloses an acoustic imaging system that includes an ultrasonic transducer which generates plane waves through a deformable membrane and into one side of an object. Another deformable membrane contacts the other side of the object, for coupling ultrasonic energy passing through the object into a container that contains a liquid coupling medium. Ultrasonic plane waves are directed through the liquid coupling medium to a liquid/gas interface surface of the liquid coupling medium, referred to as a hologram detection surface. A coherent light beam from a laser is used to illuminate the hologram detector surface to generate a diffracted optical image that is filtered and supplied to a viewing lens. Thus, the Garlick patent discloses use of a complex acoustic imaging device which uses laser illumination of a single liquid/gas interface to produce an object image. It would be desirable to provide an acoustic imaging system which can be implemented in a compact, cost effective manner, which achieves high image resolution without detrimental speckle noise, and which avoids the complex configuration of systems such as that disclosed by Garlick.
The present invention is directed to reduction and/or elimination of speckle noise and other undesirable characteristics associated with acoustic imaging, while maintaining and/or improving the image resolution achieved by a compact, cost-effective system.
Exemplary embodiments of the invention relate to methods and systems for acoustic imaging. An exemplary acoustic imaging system comprises: a first transducer for generating an unfocused acoustic beam and for directing the unfocused acoustic beam into a target; and an acoustic lens system for focusing a portion of the acoustic beam received from the target onto an imaging array, said imaging array comprising a two dimensional array of acoustic to electrical transducers which produce electrical signals in response to the portion of the acoustic beam received by the imaging array. Speckle noise reduction is accomplished, at least in part, via combination of the unfocused acoustic beam, the acoustic lens and the two dimensional imaging array, by which an incoherent beam received from a target is focused onto the surface of a two-dimensional imaging array or discrete acoustic to electrical transducer.
In one exemplary embodiment, a portion of the acoustic beam transmitted through at least a portion of the target is received by the acoustic lens (transmission mode).
In alternate embodiments, a portion of the acoustic beam reflected from the target is received by the acoustic lens (reflection mode).
Exemplary embodiments also include an imaging array having a semiconductor material upon which the piezoelectric material is formed.
Exemplary embodiments can be implemented in a cost-effective and compact manner suitable, for example, as a hand-held device.
In alternate embodiments, an interface is provided for the acoustic imaging array, the interface being a solid material that is transmissive to acoustic energy, and that is placed in contact with an exposed surface of the imaging array to couple acoustic energy onto the imaging array.